How pure is semen, and is it considered impure if it becomes wet after drying, and how can one get rid of the obsessive thoughts related to this?

Semen is pure according to the most preponderant opinion of the scholars. Therefore, it is not necessary to wash the bed or wipe the floor if semen gets on them. The body of a person in a state of major ritual impurity (junub) is pure, and there is no justification for wiping the door. The sister who asked the question should cast away these whispers and delusions from herself.